1. Field of the Invention
The invention relates to a process for the manufacture of multilayer pc boards having conductive patterns located in at least three planes, in which at least two laminates, superimposed upon each other and separated by at least one prepreg, are aligned relative to one another by means of a register-hole system with which the laminates are provided in their peripheral zones, said laminated structure being subjected to the curing process under heat and pressure.
The invention also relates to a special laminated structure which is produced by this process and which constitutes an intermediate stage during the manufacture of multilayer pc boards incorporating the invention, as well as the use of same in the aforesaid manufacturing process.
"Multilayer pc boards" (multilayers) are understood to mean a laminated structure comprising two or more laminate layers, e.g. thin mold mats impregnated with epoxy glass (thin laminates), each having one or two etched conductive patterns separated by prepregs, e.g. mold mats impregnated with epoxy glass advanced in cure only through the so-called B-stage, said laminated structure being bonded together into one unit by curing in a press under heat and pressure.
Multilayer pc boards of this kind are used in professional electronics.
2. DESCRIPTION OF THE PRIOR ART
In a prior art process for fabricating multilayer pc boards, the proper arrangement of the laminates, and therefore of the conductive patterns, as well as the compression molding together with the prepregs under heat and pressure, are carried out in a single operation. To accomplish this, the compression molds are provided with dowel pins on which the laminates are placed with their register holes, whereupon the laminated structures thusly secured in position in the compression molds are subjected to the molding operation in the press. In this so-called pin-lamination process, it is a disadvantage that, like the laminates, the compression molds and all the auxiliary equipment, such as pressing plates, pressing cushions and foil insulants, must also be provided with register holes for the dowel pins, which entails considerable expense. In addition, the compression molds reduce the useful holding capacity of the press and increase the amount of heat required for the curing. Another drawback is that for the manufacture of multilayer pc boards having different sizes, one must make and keep on hand appropriately matched molds, including the aforementioned auxiliary equipment, or in the case of a standard mold matched to the pressing die, more material will be wasted because of the low level of utilization. In both instances, the cost of the product will be considerably increased.